The drive for energy-efficient building comes down to a quest for the so-called tight envelope. In builder lingo, the better a structure keeps out the wind and the rain, the tighter its envelope.

And if you can achieve that tight envelope while using some kind of renewable, recycled material, then that's all the better. But while many new energy-efficient products enter the market each year, some builders shy away from them because of higher costs. In many cases, just adding a layer of insulation or a specially glazed window can increase the cost of materials by 20 to 30 percent.

But in most cases, experts in energy conservation argue that more efficient materials will lead to lowered costs of heating and cooling a house, so the homeowner will recover that money, usually within several years.

Let's take a look at some of the latest energy-efficient building materials on the market right now.

10

Recycled Steel

If you check out the material produced by the SteelRecycling Institute (SRI), you might want to skip the wood beams when building your next house.

According to the SRI, builders are simplifying the framing process by ordering customized steel beams and panels to fit each specific design. The SRI touts the durability of steel in areas subject to high winds and earthquakes. Further, it reports that while a 2,000-square-foot (186-square-meter) house requires 40 or 50 trees to build, a frame from recycled steel would require no more than the material that comes from six scrapped cars [source: Steel Recycling Institute].

At least 65 tons (59 metric tons) of scrap steel are recycled every year. Recycling scrap reduces the energy produced in making the steel by 75 percent, and it saves space in landfills as well [source: Steel Recycling Institute].

9

Insulating Concrete Forms

With this type of construction, workers pour concrete into forms that act as insulation.

This is a 60-year-old technology that's enjoying new life with the discovery of its energy-saving properties.

The Portland Cement Association, one of the top makers of concrete forms, defines them as "cast-in-place concrete walls that are sandwiched between two layers of insulation material." Concrete is poured into forms that serve as insulation layers and remain in place as a permanent part of the structure. The technology is used in freestanding walls and building blocks.

An industry-funded study by the Massachusetts Institute of Technology issued a report in late 2010 that said buildings made from insulated concrete forms saved 20 percent over the energy consumed by wood-frame buildings in cold climates such as Chicago [source: Ochsendorf].

8

Plant-based Polyurethane Rigid Foam

After the No. 1 maker of surfboard material went out of business and was fined by the Environmental Protection Agency for using a toxic chemical, a surfboard maker in San Diego started producing a foam material that comes from plants.

Ned McMahon, chief operating officer of Malama Composites, is manufacturing the foam from materials such as bamboo, hemp and kelp.

The so-called rigid foam is used in insulation, wind turbine blades, furniture and, of course, surfboards.

When used as insulation, the foam offers high moisture and heat resistance, excellent acoustics and protection against mold and pests. It also has a higher R-value than fiberglass or polystyrene, meaning that it has a higher thermal resistance and insulates better [source: Malama Composites].

7

Straw Bales

A home built primarily from bales of straw can be stronger than you may think.

Ever build with LEGOs? Then you can build a house. That's the philosophy of Mark Jensen, who supervises the building of straw bale houses for Native American communities. Straw is a byproduct of the grain industry that often would be burned otherwise.

According to the California Straw Building Association, straw, if kept dry, can last for thousands of years. Straw bales bond well to stucco and plaster walls, and they provide good insulation.

Straw bales usually weigh 50 to 90 pounds (23 to 41 kilograms) each, and a 2,000-square-foot (186-square-meter) house needs about 300 medium-sized straw bales for its construction. Although few jurisdictions account for straw bale construction in building codes, local authorities manage the construction on a case-by-case basis [source: NAHB Research Center].

6

Cool Roofing

The Cool Roof Rating Council explains it like this: If you want to stay cool on a hot day, it's better to wear a white T-shirt than a black one because it reflects rather than absorbs heat. A cool roof is like that white T-shirt: It reflects heat from the sun and stays cooler, thus transferring less heat into the building.

In the past, the roofing materials themselves needed to be light-colored for this concept to work. But new treatments allow consumers to choose darker materials that will reflect heat back into the atmosphere, as well.

Without question, these materials cost more than traditional roofing. Eco Home Magazine cited one estimate at $80 per square foot more. Of course, experts argue that a lower electric bill in the blazing days of August will help you recoup those costs quickly.

5

Structural Insulated Panels

Insulating panels made from foam can help save up to 50 percent in energy costs over other materials.

Think of an Oreo cookie, and you've got the idea about a structural insulated panel (SIP). SIPs are made from a layer of foam insulation that's sandwiched between pieces of plywood, strand board or cement panels.

In 2009, the material was used in less than 2 percent of new homes.

By some estimates, SIPs save 50 percent in energy costs over houses built from conventional materials [source: NAHB Research Center]. But some people think they're ugly, and architects generally don't have much experience using the material.

According to the National Association of Home Builders, the material is fire resistant, and it can be used for foundations, floors, basements and load-bearing walls. And as to the aesthetic issues, the association's research notes that the surfaces can be given finished looks, such as wood grain or stucco. Siding, bricks and stone can be installed on the panels, too.

4

Recycled Wood/Plastic Composite Lumber

Ever wonder where those plastic bags go? If you've recycled them, they may turn up in the construction of your next deck or on the local playground.

According to the National Association of Home Builders, this 50-50 combination of wood fibers and waste plastics is more durable and less toxic than conventional treated lumber. The material is also more rigid than pure plastic lumber because the wood fibers add extra strength.

While it's more resistant to mold and rot, the composite lumber is more rigid in the cold and more pliable in the heat than plastic lumber. It's also significantly more expensive than conventional treated lumber products.

The "E" in low-E stands for emissivity, and a clear coating of metallic oxide on these windows keeps the heat inside the house in the winter and outside in the summer.

Typically, this coating is used on external storm windows in houses that don't have double-pane windows. The technology comes in soft coatings and hard coatings. The soft coatings go between layers of glass, while the hard coatings go on the outside.

Low-E windows typically cost between $60 and $110 each. That's 10 to 15 percent more than clear glass storm windows, but they definitely have benefits: They can reduce heat flow through the glass by half, and that will help reduce heating costs by 10 to 20 percent [source: NAHB Research Center].

2

Vacuum Insulation Panel

In a 1-inch (2.54-centimeter) panel, the vacuum insulation panel (VIP) provides as much as seven times the insulating protection as traditional products [source: NAHB Research Center]. This technology may well be the ultimate insulation panel. However, it's currently only available for commercial industrial refrigeration and specialized container systems.

The VIP looks like something out of the old NASA films about spacecraft technology. It's a textured silver rectangle that holds a core panel enclosed in an airtight envelope. Manufacturers can make the panels in any size.

The National Association of Home Builders reports that the biggest installation problem is the panel's fragile surface, which has to be encased in a protective covering. The association is working with The Dow Chemical Company, the chief manufacturer of the product, to make the panels available as insulation for attics in future residential construction.

1

Earth

Adobe construction has been used for centuries, but there are currently no codes in the U.S. for building with this material.

If you want to build with walls of rammed earth or adobe, the great advantage is that the material is abundant, free and doesn't have to be transported to the job site. The downside is that you'll have a hard time finding specialized craftsmen who know how to build with dirt.

Countries including China, Peru and New Zealand actually account for this type of building in their codes, but the United States has not established codes for building from the earth. The difficulty of finding craftsmen who can do the job led the National Association of Home Builders to estimate that costs for labor could run at least $80 per square foot.

Even so, researchers at the association note that earthen walls provide excellent thermal mass, and the material comes from the ultimate in renewable sources.

Check out the links on the next page for lots more information on eco-friendly building.